Piercing is a machining technique involving punching a hole in a workpiece such as a metal sheet. A piercing apparatus typically includes a piercing punch and a piercing die. A workpiece is placed on the top stage of the die that has a piercing hollow therein, and the tip of the piercing punch is pressed onto the workpiece so as to make a hole in the workpiece by punching off the corresponding piece. The shape of the hole can be made to be a circle, an oval, a square, a rectangle, a star, a triangle, a hexagon, a polygon, etc. by selecting the cross-sectional shape of the piercing punch and the piercing hollow according to the needed shape. There are a variety of piercing operations, including but not limited to: perforating that involves punching a large number of closely spaced holes; notching that removes material from the edge of the workpiece; and nibbling that cuts off material with a contour by producing a series of overlapping holes, slits or notches, allowing for complex shapes to be formed in the workpiece. These punched-off pieces are scraps that need to be discarded properly. In a conventional piercing process, however, it is often the case that, due to magnetization, static-electricity or vacuuming effects, these scraps get attached to the tip of the piercing punch, thereby interfering with the subsequent punching operation, or fall off from the tip and attached to the vicinity of the newly formed hole, thereby requiring cleaning of the product.